Pick for access
Choose the database that matches how your app reads and writes data. Do not choose only because a tool is popular in your college group.
If your data has strong relationships and you need reliable transactions, start with SQL. If your data shape changes often and reads are mostly by document, consider NoSQL.
When SQL fits
SQL databases like PostgreSQL and MySQL store data in tables. They are good when your app has clear entities and relationships: users, orders, payments, bookings, teams, submissions.
Use SQL when you need joins, constraints, and transactions. For example, a UPI split app should not mark a payment as settled unless the related payment record is also saved correctly.
When NoSQL fits
NoSQL databases like MongoDB and Firebase Firestore store flexible documents or collections. They are useful when each item may have different fields, or when you want to move fast with changing screens.
Use NoSQL when your main read is usually one document or one collection query. For example, a campus notice app can store notices with optional fields like clubName, eventDate, imageUrl, and tags.
Decision steps
Do each one yourself, then tap it to tick it off. The ticks are only a checklist for you: they are not marked or scored.
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Avoid vague reasons
Do not write, “We used MongoDB because it is scalable.” That does not defend your design. Almost any database can scale enough for a hackathon if used well.
Write the reason from your app’s access pattern. Mention what you gain and what you give up.
Design note example
Add a short note like this in your README or system design section. Keep it specific to your project.
Database choice
We use PostgreSQL for this food pre-order app.
Main data:
- users
- canteens
- menu_items
- orders
- order_items
- payments
Why SQL:
- Orders have clear relationships with users, menu items, and payments.
- We need transactions so an order and its order items are saved together.
- We need queries like: show all orders for one user, show pending orders for one canteen, and calculate daily sales.
Trade-off:
- Schema changes take more planning than MongoDB.
- In return, we get safer relationships and easier reporting queries.Use AI carefully
You can ask an AI tool to compare SQL and NoSQL for your app. Give it your screens, data, and queries. Do not accept a generic answer.
Check if it mentions your actual read and write patterns. If it only says “NoSQL is scalable” or “SQL is structured,” ask it to rewrite using your project details.
Prompt:
I am building a hackathon app for college mess pre-ordering.
Screens: menu list, cart, order status, admin order dashboard.
Data: users, menu items, orders, order items, payments.
Main queries: show menu by canteen, create order with items, show pending orders for admin.
Should I use PostgreSQL or MongoDB? Give a short design note with 2 trade-offs.Do this now
Do each one yourself, then tap it to tick it off. The ticks are only a checklist for you: they are not marked or scored.
0 of 5 done